The brazillian butt lift uses relatively large volumes of transplanted fat to create a more full, lifted buttocks.
The problem with using something other than autologous tissue (and fat is usually something that most patients don't mind having removed).
Fibrel is porcine collagen and injecting that much of a non-native material would likely cause problems such as increased infection rate, pain and scar tissue formation. In addition all collagen products resorb more than autologous fat meaning that the look you get to start with may not be the look that you end up with.
In my practice I only use liposuctioned fat for a safe lasting result.
Hope this helps.